Method for producing anisotropic magnetic powder, and anisotropic magnetic powder

Abstract

Provided is an anisotropic magnetic powder having a low oxygen concentration, a small average particle size, a narrow particle size distribution, and a high remanence, and a method for producing the anisotropic magnetic powder. The present disclosure relates to a method for producing an anisotropic magnetic powder, including: pretreating an oxide containing Sm and Fe by heat-treating the oxide in a reducing gas atmosphere to obtain a partial oxide; heat-treating the partial oxide in the presence of a reducing agent to obtain alloy particles; nitriding the alloy particles to obtain a nitride; and treating the nitride with an alkali to obtain a magnetic powder.

What is claimed is: 
     
         1 - 5 . (canceled) 
     
     
         6 . A method for producing an anisotropic magnetic powder, comprising:
 pretreating an oxide containing Sm and Fe by heat-treating the oxide in a reducing gas atmosphere to obtain a partial oxide;   heat-treating the partial oxide in the presence of a reducing agent to obtain alloy particles;   nitriding the alloy particles to obtain a nitride; and   treating the nitride with an alkali to obtain a magnetic powder.   
     
     
         7 . The method for producing an anisotropic magnetic powder according to  claim 6 ,
 wherein the method further comprises treating the magnetic powder with an acid after the treating with the alkali.   
     
     
         8 . The method for producing an anisotropic magnetic powder according to  claim 7 , wherein the acid comprises at least one of hydrogen chloride or nitric acid. 
     
     
         9 . The method for producing an anisotropic magnetic powder according to  claim 7 ,
 wherein the method further comprises dehydrating the magnetic powder after the treating with the acid.   
     
     
         10 . The method for producing an anisotropic magnetic powder according to  claim 6 ,
 wherein the treating with the alkali comprises treating the nitride with an aqueous solution containing calcium hydroxide or an aqueous solution containing sodium hydroxide.   
     
     
         11 . A method for producing an anisotropic magnetic powder, comprising:
 pretreating an oxide containing Sm and Fe by heat-treating the oxide in a reducing gas atmosphere to obtain a partial oxide;   heat-treating the partial oxide in the presence of a reducing agent to obtain alloy particles;   nitriding the alloy particles to obtain a composite containing magnetic particles and contaminants including at least one of Ca3N 2 , CaO, and metallic calcium in a sintered bulk form; and   treating the composite with an alkali to obtain a magnetic powder.   
     
     
         12 . The method for producing an anisotropic magnetic powder according to  claim 11 ,
 wherein the method further comprises treating the magnetic powder with an acid after the treating with the alkali.   
     
     
         13 . The method for producing an anisotropic magnetic powder according to  claim 12 ,
 wherein the acid comprises at least one of hydrogen chloride or nitric acid.   
     
     
         14 . The method for producing an anisotropic magnetic powder according to  claim 12 ,
 wherein the method further comprises dehydrating the magnetic powder after the treating with the acid.   
     
     
         15 . The method for producing an anisotropic magnetic powder according to  claim 11 ,
 wherein the treating with the alkali comprises treating the composite with an aqueous solution containing calcium hydroxide or an aqueous solution containing sodium hydroxide.   
     
     
         16 . An anisotropic magnetic powder having an average particle size of at least 1.5 μm but not more than 7 μm as measured with a laser diffraction-type particle size distribution analyzer under a dry condition,
 wherein the powder has a span of not more than 1.6 as defined by the following equation:
   Span=( D 90 −D 10)/ D 50 
 
 
       wherein D10, D50, and D90 represent particle sizes corresponding to 10th, 50th, and 90th percentiles, respectively, in a cumulative particle size distribution by volume, and
 wherein the powder comprises Sm, Fe, N, and O and has an O content of at least 0.05% by mass but not higher than 0.65% by mass. 
 
     
     
         17 . The anisotropic magnetic powder according to  claim 16 ,
 wherein the average circularity of the anisotropic magnetic powder is not less than 0.75.   
     
     
         18 . The method for producing an anisotropic magnetic powder according to  claim 7 ,
 wherein the acid is hydrogen chloride or nitric acid.   
     
     
         19 . The method for producing an anisotropic magnetic powder according to  claim 12 ,
 wherein the acid is hydrogen chloride or nitric acid.